A seatbelt apparatus provided on a vehicle such as a motor vehicle prevents a passenger from jumping out from a seat by constraining the passenger by a seatbelt in case of emergency such as collision or the like where a large deceleration is applied to a vehicle and protects the passenger. The seatbelt apparatus is provided with a seatbelt retractor which constantly urges a spool for retracting the seatbelt in the belt retracting direction and prevents the seatbelt from being withdrawn by activating an emergency locking mechanism (ELR mechanism) upon emergency described above to lock rotation of the spool in the withdrawing direction.
As a seatbelt retractor as described above, a motor retractor that retracts and withdraws the seatbelt by rotating the spool by the drive torque of the motor is proposed in the related art (for example, see Japanese Unexamined Patent Application Publication No. 2005-35485). According to the motor retractor in this type, since a tensile force of the seatbelt can be controlled by retracting the seatbelt by the motor, a wearing mode of the seatbelt can be set variously and hence constraint of the passenger by the seatbelt can be performed more suitably and meticulously according to a traveling state or the like of the vehicle.
The motor retractor disclosed in Japanese Unexamined Patent Application Publication No. 2005-35485 employs a power transmission gear mechanism having a predetermined number of gears as a power transmission mechanism for transmitting the drive torque of the motor to the spool. By covering the power transmission gear mechanism with a cover, foreign substances are prevented from coming into contact with or entering into the power transmission gear mechanism from the outside or entering between the gears that mesh with each other, and an operation noise which is generated when the power transmission gear mechanism is operated is constrained from leaking outside.
The motor retractor disclosed in Japanese Unexamined Patent Application Publication No. 2005-35485 is not provided with spring means for retracting the seatbelt when the seatbelt is not worn, which is provided in conventional seatbelt retractors, which is not driven by the motor. A motor retractor having such the spring means is also proposed (for example, see Japanese Unexamined Patent Application Publication No. 2005-53422).
The motor retractor disclosed in Japanese Unexamined Patent Application Publication No. 2005-53422 employs the power transmission gear mechanism having a predetermined number of gears as the power transmission mechanism for transmitting the drive torque of the motor to the spool, and is provided with the cover for covering the power transmission gear mechanism for the same object as Japanese Unexamined Patent Application Publication No. 2005-35485.
However, in the motor retractor in the related art disclosed in Japanese Unexamined Patent Application Publication No. 2005-53422, a cover a is formed of a thin plate-shaped material for covering the power transmission gear mechanism and a thin plate portion b which is relatively thin is present as shown in FIG. 4. Therefore, by covering the power transmission gear mechanism with the cover, leakage of the operation noise generated in the power transmission gear mechanism toward the outside can be constrained to some extent. However, the cover itself vibrates due to vibrations generated by the operation of the motor retractor such as vibrations generated when the motor is being driven or vibrations generated when the gears of the power transmission gear mechanism are rotating, whereby noise caused by the vibrations of the cover may be generated.
As a countermeasure, it is conceivable to form the cover with a relatively thick plate-shaped material. However, when the cover is formed simply of the thick material, there may arise a problem such that the mass of material required for the cover is significantly increased.
Such a problem is dormant in the cover of the power transmission gear mechanism of the motor retractor disclosed in Japanese Unexamined Patent Application Publication No. 2005-35485 as well as in other covers of the power transmission gear mechanism of the motor retractor in the related art.